Pants specifically worn for standing or dancing when going out. If seated while wearing the Stand Up Pants, your muffin top and/or jelly rolls become much more visible. These pants also may be very tight, or the button may come undone upon the act of sitting.
Hince the name "Stand Up Pants."

Could also be used as an excuse to not sit down with a guy who is a turn off.

A portmanteau of carpe diem, a Latin phrase that means “Seize the Day!” and DM, which stands for Direct Messages. This word means seizing the day via DMs.